(1) Field of the Invention
The present invention relates to a tricycle with an electric motor in which two rear wheels are driven not only by an electric motor while providing a battery but also driven by pedals with manpower, so as to use it as a passenger tricycle or a cart.
(2) Description of the Related Art
Today, an electric car provided with a battery which does not have problems of exhaust, and a so-called hybrid vehicle with a gasoline engine and an electric motor are being developed, in view of protection of the environment, as substitutions of a car provided with an internal combustion engine which emits combustion exhaust.
The trend has been toward a vehicle with an electric motor provided with a battery, such a bicycle, a tricycle, a van, and so on.
The above-mentioned bicycle and the tricycle are provided with batteries and electric motors with an intention to utilize electric power when a load is heavy, namely, at a time of starting, or of uphill ride, etc. The applicant of this invention has suggested an electric vehicle, in which a tricycle is driven by electricity, in Japanese patent application No. 9-60009.
In this invention, the object is an electric vehicle of a hybrid-type in which electric power is the main driving force and pedal drive is the subsidiary driving force.
The tricycle driven in the above-mentioned manner is basically constructed as follows. Namely, a front wheel is rotatably mounted on a front wheel frame and two rear wheels are mounted rotatably on a rear wheel frame. The rear wheel frame is mounted onto the front wheel frame to be rotatable about a lateral axis extending in forward and backward directions of the tricycle within a range of predetermined angles, so that it may easily turn the tricycle by inclining the front wheel frame on which a driver rides. Further, the two rear wheels are driven not only by an electric motor, but also by pedals with manpower, which pedals are mounted on the front wheel frame, via a one-way clutch.
The above-mentioned tricycle with an electric motor uses a chain drive system as power transmitting means, which was normally used for a bicycle, in order to drive the rear wheels by means of the pedals with manpower, as was in the above-mentioned Japanese patent application No. 9-60009.
The chain drive system had an advantage in that up-and-down relative movements of the front wheel frame and the rear wheel frame could be absorbed (Even if the both frames were rigid, the relative movements would rise due to flexible transformation of the frames.), but it had the following problems.
Namely, in the case of the tricycle which has a wide track compared to a bicycle, in order to make a small turn smoothly by using the two rear wheels which are not provided with inclining suspensions for wheels, there is no manner except that the rear wheel frame suspending the two rear wheels may be provided rotatably about a lateral axis extending in forward and backward directions within a range of predetermined angles, so as to incline or tilt the front wheel frame on which a driver rides. Although such a construction has been used in the prior art, where the front wheel frame is inclined sufficiently at angles of 10 to 20 degrees in order to make a small turn, it frequently causes the chain slip off of the sprockets.
If the inclination of the front wheel frame is minimally controlled in an attempt to prevent such trouble, the turning performance of the tricycle goes down greatly and a small turn cannot be smoothly carried out.
By the way, functional and structural advantages of a vehicle with an electric motor are that operation can be done only by controlling a starting switch of an electric motor, and that the structure is extremely simple. How the other structures necessary for running can be similarly simplified is at issue. In order to provide such simplification, also with regard to a brake mechanism, such systems separated from a driving system of the electric motor are adopted such as a hand brake which mechanically (a release wire, etc.) and directly works on wheels, a pressure-type brake (a type which is adopted by a front wheel of an ordinary bicycle, etc.), and a disc brake (a kind of a pressure-type).
By adopting the separated system with a simple structure such as mentioned above, a speed can be reduced only by operation of a brake lever while the starting switch (or an accelerator for adjusting a speed, voltage control, etc.) of the electric motor is left untouched, and a starting condition is restored only by releasing # the brake lever. Thus, the tricycle with the electric motor can be driven with an extremely simple operation.
In this invention, the following study on the tricycle with an electric motor was developed first, on the premise that the advantages of the vehicle adopting such a simple structural system is utilized.
Namely, the tricycle with an electric motor is constructed in which generating power of the electric motor is reduced to a necessary number of revolutions via a speed reducer, the generating power of the speed reducer is transmitted to two rear driving wheels via a transmission means, a one-way clutch is mounted to each of drive transmission systems between the speed reducer and the two driving rear wheels which drive transmission systems transmit only the generating power of the electric motor, and the two driving rear wheels are mechanically braked by operation of the brake lever.
The speed reducer is necessary for obtaining necessary torque for running (load carrying or traction) from a small-sized electric motor, and the tricycle is constructed to be a two-rear wheel drive because of the rear wheels which receive drive resistance (traction resistance) in a preferable form to make best use of the drive.
In the meantime, in the two-rear wheel system, when the tricycle makes a turn the tricycle does not turn smoothly unless the numbers of rotating of an inner wheel and an outer wheel differ due to the difference between the respective radii of the wheels.
The above-mentioned problem has been solved by driving the right and left wheels by use of a differential gear mechanism, however, since the differential gear mechanism is expensive, application of the same to this invention, whose object is a simple and inexpensive tricycle, raises costs.
According to this invention, as an alternative means to the above, the problem was solved by introducing a one-way clutch into each of the two wheels and by adopting a method of stoppage of the electric motor (brake of an electric current).
Namely, according to this invention, directing attention to the fact that the speed of the tricycle is reduced by operation of the brake when linear running is shifted to curve running, the brake lever and the switch of the electric motor are so interlocked that the electric current to the electric motor is broken when the brake lever is operated.
Thereby the speed of the tricycle is reduced by the brake lever, the drive of the electric motor is stopped at the same time, and the two wheels become free-wheeling. When a handlebar is turned under this condition, ground resistance of the inner wheel increases, however, since the two wheels are free-wheeling, necessary number of rotation of each of the right and left wheels can be obtained and smooth turning can be achieved.
Though smooth turning with simple operation and inexpensive structure are achievable by the above-mentioned introduction of the one way clutch to the two driving wheels and the adoption of the method of stoppage of the electric motor (brake of an electric current), a new problem, as mentioned below has occurred.
Namely, when the turning which is preformed by the above-mentioned operation finishes and linear running starts or when re-drive (acceleration) becomes necessary, it is difficult to obtain a condition of a smooth acceleration or a condition of a powerful drive even if electric current is resumed to the electric motor by releasing the brake, wherefore it becomes very difficult to revert from a curve running to a linear running, which therefore results in a problem in safety.